In the past, antimicrobial drugs have been directly applied onto the injured part of the body. Recently, depending on the type of wound, medical wound dressings, such as medical tape, patch, gelatin film bandage and band-aids, have been adopted to cover the wound, thereby, isolating the wound from improper contact with the external atmosphere, protecting the wound, preventing infection, and reducing pain.
It is known that the use of noble metals such as silver, gold, palladium, platinum, copper, and zinc in dressings, have effectively killed microbes. The use of such noble metals in dressings has been disclosed in many references. For example, Robert Edward Burrell et al. (U.S. Pat. No. 6,692,773 B2) disclose the use of a noble metal such as silver, gold, palladium, or platinum, or an alloy or a compound thereof, in a nanocrystalline form with a grain size of less than 100 nm, in coating a fabric to provide a dressing having the antiproliferative effect. Widemire (U.S. Pat. No. 5,782,788) discloses the fixation of a silver foil layer on a gauze pad to inhibit the growth of bacteria, virus, and fungus. Fabo (U.S. Pat. No. 5,340,363) discloses a dressing comprising an outer absorbent layer and an inner porous hydrophobic layer knitted of elastic threads and encapsulated by a soft hydrophobic silicone or polyurethane gel, wherein the gel can be used as a carrier for an antibacterial agent (e.g., zinc), a pain-relieving substance, and an agent that stimulates wound repair.
Klippel et al. (U.S. Pat. No. 3,830,908) disclose the use of micronized allantoin as a carrier for a bactericidal or bacteriostatic ingredient (such as silver citro allantoinate). The composition is dispersed on the surface of a plastic air splint or other bandaging product to provide antibacterial action, depending on the molecular dissociation. McKnight et al. (U.S. Pat. No. 3,800,792) disclose a surgical dressing comprising a layer of tanned and reconstituted collagen foam film, which is laminated to a thick continuous layer of an inert polymer. The collagen layer contains a finely-divided silver metal added by soaking the collagen film in Tollen's reagent. Stowasser (U.S. Pat. No. 2,934,066) discloses a dressing of absorbent metal-coated fibers, such as a carding fleece coated with aluminum and backed by compressed cellulose, and polyamide fibers coated with vacuum-deposited silver.
Given the prior technology mentioned above, it is clear that antimicrobial noble metals are widely used in therapy, especially in dressing. However, the use of these noble metals still focuses on the noble metal alone and at most, the noble metal in a form of an alloy or compound. Although such use can provide an antimicrobial effect, the microbes are only destroyed upon “coincidentally” contact with the noble metal. Because of this, the noble metals merely provide a “passive” antimicrobial effect.
Moreover, as known by persons having ordinary skill in the art, the above-mentioned noble metals can only fight microbes in the presence of moisture. Therefore, for practical use, the medium must always be moist. If necessary, water is added to provide a moist environment. For example, according to U.S. Pat. No. 6,692,773 B2, when a nanocrystalline noble metal is coated onto a dressing for topical use on skin, the dressing must maintain a moist condition for the noble metal to exhibit the desired efficacy (see column 6,line 64 to column 7,line 17). Consequently, U.S. Pat. No. 6,692,773 B2 further discloses the preference for an absorbent layer in the dressing to hold in moisture for activating the noble metal (see said patent, column 5,lines 33 to 37). Such need of moisture for activating noble metals can also can be found in other references, such as the content published via the website, http://www.burnsurgery.org/Modules/silver/images/section7b/Mid_partial_thickness3copy.ipg.
The present invention relates to an improvement of the therapeutic application of a noble metal that has an antimicrobial effect. The present invention actively aggregates and then destroys microbes so as to effectively reduce, and even prevent, the microbial infection.